(1). Field of the Invention
The present invention generally relates to an air bag system which is installed in an automotive vehicle to provide protection for a driver or passengers against the impact of a collision. More particularly, it relates to a venting device of an air bag system which has vent holes, opened and closed variably according to the velocity of collision to provide the best possible air bag performance, and prevents a gas leakage of the air bag at an initial stage to enhance the effect of earlier restraint.
(2). Description of the Prior Art
An air bag system serves as an auxiliary device of a seat belt in order to protect a driver or passengers with safety in case of sudden collision. The air bag system consists of an air bag module having an air bag, an inflator, a gas generator, and a pat cover, and a front impact sensor, a rotary contact switch, an alarm lamp, and a calculator. Thus, if the automotive vehicle collides with another automotive vehicles during running at a specified speed, a safety switch and the front impact sensor are turned on, and simultaneously with triggering the inflator, the air bag is rapidly inflated with gas, generated from this inflator, and is deflated after it runs into a driver's face or a passenger's to provide cushioned protection for him or her.
The air bag is a round-shaped bag made of rubber-coated nylon, and its capacity is 50 to 60 R. The air bag is installed on the inflator, being folded, and is rapidly inflated with nitric gas produced from the inflator.
The conventional air bag system will be more fully described referring to FIG. 1.
The conventional air bag system includes an air bag 50 with vent holes 60, an inflator 51 having gas outlets 51a to instantaneously ignite a gas generator charged in it and generate nitric gas, thus inflating the air bag with the nitric gas, an inner panel 52 integrally formed with the inflator 51 and an outer panel 54 inserted between the inner panel 52 and coupling panel 53 and coupled therewith by fixing means.
In case of sudden collision, the nitric gas, produced from the inflator 51, flows into the interior of the air bag 50 through the gas outlets 51a, and inflates the air bag 50 rapidly, thus early restraining the driver or passengers. As the air bag 50 runs into him or her, it absorbs the shock and the gas inside of the air bag is continuously discharged to the outside through the vent holes 60 so that the air bag 50 is deflated.
In order that the air bag provides more efficient protection for the driver or passengers against the impact of a collision, the air bag must be unfolded very quickly to restrain a driver or a passenger earlier and have a long distance of variation with a given pressure once the driver or passengers is restrained. The vent holes serve to discharge the inner gas in order that the air bag, providing cushioned protection for the driver or passengers, has a long distance of variation. However, the conventional vent holes are formed at the bottom of the air bag, and when the air bag is inflated, the gas is discharged to the outside through the vent holes, which decreases a speed at which the air bag is inflated with gas, thus obstructing the earlier restraint of the driver or passengers. Thus, it is preferable that the vent holes are closed at the time when the air bag is unfolded, and are opened to a certain degree in proportion to the pressure increase so as to properly absorb the impact created when the air bag runs into his or her face after it has been unfolded.
As described above, the conventional vent holes 60 are formed in the air bag 50 to a specific size, and the nitric gas, flowing into the air bag 50 in case of collision, is discharged to the outside through these vent holes 60, thus making the air bag 50 be slowly inflated with the gas and interfering with earlier restraint of a driver or a passenger. The gas is discharged to the outside through the vent holes that are opened to a certain extent regardless of the velocity of collision, which deteriorates the passenger safety.